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Weight Loss NHS
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How accurate is the BMI ?

I think many factors have to be taken into consideration when a system like the BMI measures a person's weight. These factors include, but not limited to, the bone mass and structure, muscles mass, and the variety of weight scales in the market. In other words, two people who have the same height, weight and, as a result, BMI might differ in their health and body figures which shows whether someone is visually overweight or not.

Hence, is there any better measurement to accurately calculate the weight someone has to lose or even gain ?

p.s. I'm new here

7 Replies

Hi Moseleys

Welcome to the weight loss forum.

Take a look at the Welcome Newbie post in the Pinned post section at the right hand side or at the bottom if your on a mobile. Have a look at the nhs 12 week plan, many members have had success following this plan. Use the BMI checker to work out your daily calorie allowance.

Below the Pinned posts are the Topics where members share a range of weight related subjects.

Take your measurements at the start together with a photo so you can see the changes on the days the scales don't move.

We have daily weigh ins so why not come along and join us. You can find the weigh ins on the Home page in the Events section on the right. Just click on the post in Events and record your start weight and any loss/gain or maintain for the week.

To get the most of the forum be active, share tips, recipes and experiences. Read some of the posts they are very motivating.

Have a good first week.



Hey, I think the BMI is rubbish. Its fine when someone is Obese to give them a visual sign that they are obese but to me having to buy size 50 trousers might have been a better indication that your weight is an issue lol! Like all these things that are generic it is too narrow a description and it does not take into account muscle mass either. So I have a very bad BMI. But my body fat percentage is currently 19% so how am i overweight? It is of course because I have a bit of muscle hanging off my bones.

To me the most critical and important measurement stats are your body fat %. Then the scales. I currently am trying to keep the same weight and muscle tone that I have now but want to drop down to about 12-15% body fat. With that in mind we store most of our fat round our middle, and our hips. So if I measure my waist and hips before I start to modify my diet and every couple of weeks if that tape measurement is getting smaller I know I am losing FAT.

Some of these new digital scales have body fat % measurements and all sorts of other fancy stuff. Well worth investing in. But the most important item in your weight loss journey? How do I look in the mirror? Are my clothes feeling looser? can I get into those trousers I last wore on holiday 10 years ago? will flares every come back into fashion?


Hi Moseleys, I recently got excited about the waist to height ratio, but again it has its limitations... healthunlocked.com/nhsweigh...


As you quite rightly state, the BMI scale isn’t a true measurement/reflection of one’s health, nor is the weight presented by the weighing scales, since neither take into account skeletal density or the ratio of lean mass to body fat, for example.

By the BMI scale, I’ve been obese since my early twenties, but that’s largely due to my gym activity and regular running.

Do I worry about satisfying the recommendations of an antiquated scale, based upon my current weight and height? Absolutely not.

Instead, I measure my health upon ensuring that consumption of refined carbohydrate remains at an absolute minimum, while also ensuring that daily intake is consummate to my level of activity, based upon BMR and TDEE.

On days that I don’t exercise (2 in 7), I simply reduce intake accordingly, to ensure that current weight is maintained and not gained (otherwise known as calorie cycling).

Other factors that I measure my health and fitness by include the speed that I’m able to perform high intensity intervals (owed, in part, to mitochondrial activity of the heart) or the duration that I’m able to maintain a set running pace, for example.

Additionally, the speed at which HR returns to near resting levels after cardiovascular exercise is also another indicator of overall health.

In response to your question over how best to lose/gain weight, familiarising yourself with BMR/TDEE calculators (Miflin St. Jeor method) will stand you in good stead, since they’ll allow an appreciation to be gained of how many calories ought to be consumed, to maintain current weight (TDEE), so that the correct daily calorie deficit can be maintained, promoting healthy and sustainable weight loss.

For example, let’s say that you were lightly active (exercising 1-3 times per week) with BMR amounting to 1600Kcal and TDEE 2200Kcal. By maintaining a daily deficit of 400Kcal from TDEE, the body would need to release the same amount from existing fat reserves to fuel exercise, on top of those it’d usually expend on a daily basis.

Over the course of 7 days, through a mixture of calorie reduction, exercise and routine activity, the overall deficit may amount to 7000Kcal. Given that a lb of fat contains around 3500Kcal, the overall deficit of 7000Kcal translates to a 2lb reduction in body weight.

Granted, a 2lb reduction may not appear to be a great return in exchange for the effort applied, but also bear in mind that regular exercise serves to improve the shape, definition and density of muscle mass (even in deficit), so its increasing prominence will partially off-set the numbers upon the scales.

Instead, use an improving body composition and increased energy levels to be your greatest indicator of success. If clothing begins to fit and flatter far better than it once did, or you appear thinner upon glancing in the mirror, your eyes probably aren’t deceiving you.

Quite simply, if the above begins to occur (which I’m sure it will), your efforts will be working in a way that cannot be wholly translated by the BMI scale or by the set kept in the bathroom.

1 like

You're right it's a completely individual thing and in the end you learn the most about your loss from the tape measure and clothes size. I'm at the very top of the acceptable end of a healthy bmi and " ought " to be a stone lighter. But having lost over 2 stone from size 16 I am now a 10/12 and I know I could neither comfortably lose another stone nor keep it off. It's got to be realistic or it'll all just pile on again. Fitting into something is the best feeling and that's what motivates many to keep going!!


I'm the same I'm on cusp of healthy/overweight bmi but can wear clothes from size 8 to size 12. I've turned to the waist to height ratio instead and am using a tape measure instead of scales, as I was torturing myself about wanting to be in the 9s rather than the 10s, just to be a 'healthy' bmi...


Yes I would have loved to have got into the 9s , it's such an extraordinary feeling seeing the change in numbers and gives such a boost. But no matter how strict I was about food I couldn't seem to get there and I'm now reconciled to being happy where I am and knowing I'm fit . It can become obsessive and you can lose sight of where you've come from. It's enough of a challenge maintaining and enjoying food without it needing to rule your social life!


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